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We study collective excitation modes of a fermionic gas of $^6$Li atoms in the BEC-BCS crossover regime. While measurements of the axial compression mode in the cigar-shaped trap close to a Feshbach resonance confirm theoretical…

Other Condensed Matter · Physics 2007-05-23 M. Bartenstein , A. Altmeyer , S. Riedl , S. Jochim , C. Chin , J. Hecker Denschlag , R. Grimm

We examine the superfluid and collapse instabilities of a quasi two-dimensional gas of dipolar fermions aligned by an orientable external field. It is shown that the interplay between the anisotropy of the dipolar interaction, the geometry…

Other Condensed Matter · Physics 2008-12-11 G. M. Bruun , E. Taylor

This thesis presents theoretical work in s- and p-wave resonantly paired Fermi gases at zero temperature. In the BEC regime of the wide-resonance s-wave BCS-BEC crossover, the chemical potential, speed of sound, condensate depletion, and…

Superconductivity · Physics 2008-07-18 Jesper Levinsen

We report on the observation of the Josephson effect between two strongly interacting fermionic superfluids coupled through a thin tunneling barrier. We prove that the relative population and phase are canonically conjugate dynamical…

We determine the size of the critical region of the superfluid transition in the BCS-BEC crossover of a three-dimensional fermion gas, using a renormalization-group approach to a bosonic theory of pairing fluctuations. For the unitary Fermi…

Quantum Gases · Physics 2016-03-08 T. Debelhoir , N. Dupuis

In quantum many-body systems with spontaneous breaking of continuous symmetries, Higgs modes emerge as collective amplitude oscillations of order parameters. Recently, Higgs mode has been observed in the ultracold Fermi gas. In the present…

Quantum Gases · Physics 2019-01-30 Jun Tokimoto , Shunji Tsuchiya , Tetsuro Nikuni

We consider a two-component gas of fermionic atoms confined to a quasi-two-dimensional (quasi-2D) geometry by a harmonic trapping potential in the transverse direction. We construct a mean field theory of the BCS-BEC crossover at zero…

Quantum Gases · Physics 2014-03-04 Andrea M. Fischer , Meera M. Parish

We study pseudogap behaviors of ultracold Fermi gases in the BCS-BEC crossover region. We calculate the density of states (DOS), as well as the single-particle spectral weight, above the superfluid transition temperature $T_{\rm c}$…

Quantum Gases · Physics 2015-05-13 S. Tsuchiya , R. Watanabe , Y. Ohashi

We investigate the non-universal behavior of the BCS-BEC crossover model at the normal to superfluid transition. By using a finite temperature quantum field theoretical approach due to Nozieres and Schmitt-Rink and by making the effective…

Superconductivity · Physics 2007-05-23 L. M. Jensen

We calculate the single particle spectral density of a normal (non-superfluid) two component gas of fermions in the BCS-BEC crossover within a T-matrix approximation. We review how non-condensed pairs lead to a spectral density reminiscent…

Quantum Gases · Physics 2015-05-20 Erich J. Mueller

We discuss the time-of-flight expansion of dilute p-wave Fermi condensates on the BEC side of Feshbach resonances, as a way to extract information about the order parameter symmetry for superfluidity. We show that the cloud profile is in…

Strongly Correlated Electrons · Physics 2008-05-22 Wei Zhang , C. A. R. Sa de Melo

We study the superfluidity of single component dipolar Fermi gases in three dimensions within a pairing fluctuation theory. The transition temperature $T_{c}$ for the dominant $p_z$ wave superfluidity exhibits a remarkable re-entrant…

Quantum Gases · Physics 2016-06-15 Yanming Che , Jibiao Wang , Qijin Chen

We consider a dilute two-component atomic fermion gas with unequal populations in a harmonic trap potential using the mean field theory and the local density approximation. We show that the system is phase separated into concentric shells…

Other Condensed Matter · Physics 2007-05-23 C. -H. Pao , S. -K. Yip

We derived the low energy effective action for the collective modes in asymmetric fermionic systems with attractive interaction. We obtained the phase diagram in terms of the chemical potentials. It features a stable gapless superfluidity…

Quantum Gases · Physics 2015-05-13 Elena Gubankova

Strong evidence for pairing and superfluidity has recently been found in atomic Fermi gases at the BCS-BEC crossover both in collective modes and RF excitation energies. It is argued that the scale for the effective pairing gaps measured in…

Superconductivity · Physics 2009-11-10 H. Heiselberg

We investigate strong coupling effects on the superfluid phase transition in a gas of Fermi atoms with a Feshbach resonance. The Feshbach resonance describes a composite quasi-Boson, which can give rise to an additional pairing interaction…

Soft Condensed Matter · Physics 2016-08-31 Y. Ohashi , A. Griffin

We report an observation of a dynamical super Efimovian expansion in a two-component strongly interacting Fermi gas by engineering time dependent external harmonic trap frequencies. When trap frequency is followed as…

Quantum Gases · Physics 2018-03-28 Shujin Deng , Pengpeng Diao , Fang Li , Qianli Yu , Shi Yu , Haibin Wu

We show how to describe the $T \neq 0$ behavior associated with the usual BCS- Bose Einstein condensation (BEC) crossover ground state. We confine our attention here to the BEC and near-BEC regime where analytical calculations are possible.…

Soft Condensed Matter · Physics 2011-09-13 Jelena Stajic , Qijin Chen , K. Levin

We discuss various superfluid properties of a two-component Fermi system in the presence of a tight one-dimensional periodic potential in a three-dimensional system. We use a zero temperature mean field theory and derive analytical…

Other Condensed Matter · Physics 2009-01-16 Theja N. De Silva

We study the evolution of the energy gap in a unitary Fermi gas as a function of temperature. To this end we approximate the Fermi gas by the Hubbard lattice Hamiltonian and solve using the dynamical mean-field approximation. We have found…

Statistical Mechanics · Physics 2009-11-13 Nir Barnea